Starting a long neglected 6.9..... - Page 2 - Mercedes-Benz Forum
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post #11 of 40 (permalink) Old 08-15-2017, 02:37 PM
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@ $500 you are in good shape for sure. If the trans went kaboom or another catastrophic failure you can make your money back and then some in parting it out.
FYI though, with the 6.9 you read the oil with the motor "full hot" and running, in the same fashion as you would read the transmission fluid. You cannot accurately read the oil with motor cold. These M100 engines are very robust and very rarely do they go tits up. The bottom end is built like a tank. Top end they do suffer from the very common valve guide wear which was a common issue of Benzes of this era. But normally you can drive the car with no major gripes because of this. Pulling the heads on this motor is $$$$ so do not even go there unless you are highly skilled as the parts alone is extremely expensive. If the chain feels loose over the sprockets then wind in a new chain as a preventative measure but again this is not a common failure point, as the tensioner is of the ratcheting type, so the chain remains tight, not like the M116/7 motors which have the non - ratcheting tensioner, and the common "death rattle" on high mileage ones on start up, with high miles on original chain - a recipe for top end to eat itself along with brittle guides.
If you need hydro suspension parts refurbed I can do that for you at a fee. Send me a PM if interested.
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post #12 of 40 (permalink) Old 08-16-2017, 06:25 AM Thread Starter
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Thanks Dikdann!! I have a feeling I'll be reaching out to you about those suspension parts.

My plan is as follows: get the car home to my shop, get everything drained and ready to try to start it, then go from there.

Is there anything I can check/clean/drain from the suspension prior to trying to start it??
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post #13 of 40 (permalink) Old 08-16-2017, 06:36 AM
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For initial startup, just make sure the hyrdo tank is full. After the engine starts, then you will get to see if the suspension rises. I'd concentrate on fresh oil and clean gas. Then turn the key!
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post #14 of 40 (permalink) Old 08-16-2017, 06:37 AM Thread Starter
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For initial startup, just make sure the hyrdo tank is full. After the engine starts, then you will get to see if the suspension rises. I'd concentrate on fresh oil and clean gas. Then turn the key!
I assumed there would be a lag in terms of the suspension rising, but do you know, since the car has sat so long on jack stands, will the suspension immediately bottom out when I lower it down? What I'm asking specifically is will I have a hard time rolling it and loading it onto a trailer?

Thanks guys!!

Sean
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post #15 of 40 (permalink) Old 08-16-2017, 08:00 AM
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yes, it will lower all the way down. I put a small block under the front cross bar so that I could still get my short jack under the car. With the car that low, sometimes the leveling valves are too far turned to activate. Pulling up and down on the fender tends to activate them. Maybe you will need to jack up and the let down until the valve take over. If you drain all the fluid from the system it can get harder to rise the first time. Search the forum for others that have gone thru the same thing.

When you take the accumulators off they will leak huge amounts of foamy fluid. the foam is the nitrogen mixed into the fluid. It will leak like a stuck pig. The fitting tend to get very stuck tight, use a torch to heat up a bit and that helps a lot.
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post #16 of 40 (permalink) Old 08-16-2017, 08:17 AM
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Rumb made all good points. For me I would just add to drain and clean the tank first. Normally the fluid is extremely dirty unless you had a fastidious owner. The fluid should be clear, at least golden in colour. What you will most likely find is a colour that looks like Coca-Cola! To drain the tank you need to remove it from the mounts (you can access the bottom mounts from the driver LHS fender well, much easier). You would also need to remove the pressure regulator from the top of the tank to do this. As Robert has stated these fittings can be hella tight after all these years. Localized heat with propane torch for sure, and you need to get some good flare/line wrenches otherwise you will round off the fittings for sure. They might even be too tight and you will have to wrench them off with vice grips, then replace with metric bubble flare brake lines. Wash the tank out with solvent or similar (kerosene etc), then mount the tank and drop in some fresh "ZH-M" fluid, about 2.5 - 3 litres from memory. You also need to replace the filter under the pressure regulator, they are super cheap and very good to replace on a regular basis. The system needs clean fluid to run well. Thus I would advocate to make sure you run as clean as you can for the first start up.
Indeed these cars sink extremely low to the ground and then you cannot move them without huge effort. Wooden blocks to start with just to give you some clearance is a good tip.
On a well sorted system, it should rise with no revving of the engine, in about 30 sec to 1 minute tops. At first the rise is slow but towards the end it rises quickly. Not rising or very slow rising usually points to a weak pump, or faulty pressure regulator or both. Pumps are a known weak spot but they can be rebuilt. Do not run ATF in the system, it will eat your seals! Once you have cracked the lines, you need to also bleed your pump. with the system down, open the connection from the pump at the pressure regulator, then point the open end of the hose into the filler hole of the tank, and start up the engine. This will cycle fluid through and purge air from the pump. Then reconnect after about minute of purge and start up.
Also a word on safety. The system runs at extreme pressure of about 2500 psi, so keep that in mind. Safety goggles and gloves are a must. Hydro oil under such pressure can pierce your skin and this can end up being fatal so be very careful!
Another very good site for 6.9 owners is www.w116.org

Last edited by Dikdaan; 08-16-2017 at 08:24 AM.
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post #17 of 40 (permalink) Old 08-17-2017, 04:36 AM
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[QUOTE=drohalloran;16420602]since the car has sat so long on jack stands, will the suspension immediately bottom out when I lower it down? What I'm asking specifically is will I have a hard time rolling it and loading it onto a trailer?

That is what the rubber suspension blocks are for if your have them. If not lengths of 2x4 can be cut and wedged in to keep the car up far enough to roll around and steer.
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post #18 of 40 (permalink) Old 08-17-2017, 11:32 AM Thread Starter
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Here's a question: can anything be decoded from this??
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post #19 of 40 (permalink) Old 08-17-2017, 12:24 PM
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Here's a question: can anything be decoded from this??
It shows some of the options like type of paint used. To get the full data card you need to contact MBUSA and give them proof of ownership.
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post #20 of 40 (permalink) Old 08-17-2017, 01:35 PM Thread Starter
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Thanks Dikdann......that's what I figured. I'll reach out to MBUSA when the docs come in
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